Wheeled vehicle transportation accounts for a major portion of global energy consumption and contributes much of the pollution and greenhouse gases produced by the world. The energy required of the propulsion system of a wheeled vehicle is determined by three factors: aerodynamic drag, rolling resistance, and the energy needed to overcome inertia to accelerate the mass of the vehicle and its contents.
Demand for increasing fuel efficiency and performance has led to the design of ever more streamlined vehicles, pressing close to the limit of practically achievable reductions in aerodynamic drag. Therefore, if further substantial reductions in the energy requirements of vehicles are to be realized in the design of vehicle bodies, improvements should include reductions in the rolling resistance and inertial mass of vehicles.
Rolling resistance is very largely due to the energy losses caused by flexing of the wheels and deformation of the surface over which the wheels roll (National Research Council of the National Academies 2006). These energy loses are directly proportional to the force pressing the wheels against the surface. That force is due to the weight of the loaded vehicle, modified by any aerodynamic force pressing upward or downward on the vehicle. Therefore, reduction in vehicle mass would reduce rolling resistance as well as inertia. However, efforts to design lighter vehicles have been limited by handling and safety problems at high speeds because reduction in the weight pressing the wheels against the road results in less traction for accelerating, turning, and braking. An aerodynamic system that would provide constant, well-distributed downward thrust at high speeds could yield some energy savings simply by making it possible to design lighter vehicles without compromising safety, maneuverability, and acceleration at high speeds. The reduced inertial mass of such a vehicle would require less power to achieve acceleration comparable to that of current vehicle designs. However, except at low speeds, rolling resistance would not be reduced. Substantially greater energy savings could be achieved by means of an aerodynamic system that adaptively provides varying amounts of vertical thrust (upward or downward) in response to driving circumstances. Upward thrust could be provided during linear cruising. Downward thrust would be provided during maneuvering, turning, accelerating, and braking. Substantial drag in addition to maximum downward thrust could be provided during strong braking and sharp turns at high speeds. A vehicle fitted with such an adaptive aerodynamic system would attain energy savings while also improving handling, safety and performance.
At least since the 1920's, some innovative racing cars have employed airfoils, known as “wings,” designed to produce downward thrust to increase traction and improve handling at high speeds. In 1928, the rocket-propelled race cars Opel RAK1 and RAK2 had stubby wings mounted on the sides of the body behind the front wheels. In 1956 Michael May added a large wing above the middle of a Porsche Type 550 car. In 1966 μm Hall mounted a large wing about a meter above the rear axle of his Chaparral 2E racing car. The angle of attack of the wings of both Michael May and Jim Hall could be controlled manually by the driver. Such manually-controlled wings would be impractical for ordinary (non-racing) vehicles, but might have led to the development of automated airfoil systems that would be practical for ordinary street and highway driving, but for the fact that, after each of the innovations of Michael May and Jim Hall, rules were developed to proscribe such continuously variable wings from racing competition. Large fixed wings are mounted above the front and middle of the relatively high power-to-weight-ratio racing cars known as sprint cars.
In recent years it has become fashionable to install a kind of “wing” on passenger cars, especially on sports cars. On such vehicles, as a general rule, a single wing, cambered to generate down-thrust, is located above and across the rear edge of the upper surface of the car. In this location, well behind the rear wheels, the wing levers upward on the front wheels, reducing the traction of the front wheels at high speeds. Because most modern automobiles use the front wheels for propulsion a well as for steering and braking, wings in this location diminish automobile performance as well as safety, handling, and fuel efficiency. Additionally, in this location, wings obstruct somewhat the rear view of the driver, further degrading safety. U.S. Pat. No. 5,419,608 issued May 30, 1995 to Takemoto disclosed the positioning of fixed airfoils on the underside of an automobile, between the wheels. In that location, restricted space and turbulent air flow among the steering, suspension and propulsion mechanisms of the vehicle severely constrain achievement of even the limited purposes of such fixed airfoils. As with that patent, designs disclosed in other patents as well as airfoils actually installed on modern cars are generally fixed or may be adjustable, but are not designed to be under continuous adjustment by the driver or by some automatic system such as the vehicle computer. An exception is an air brake U.S. Pat. No. 6,540,282 B2 issued Apr. 1, 2003 to Pettey. This airbrake provided only one (air braking) of the numerous advantages of the present invention. Another exception is a rear end spoiler incorporating an adjustable wing, disclosed in U.S. Pat. No. 7,226,117 issued Jun. 5, 2007 to Preiss, the sole purpose of which is to reduce drag by controlling air flow at the upper rear edge of vehicles of the station wagon or hatchback type. U.S. Pat. No. 7,264,300 issued Sep. 4, 2007 to Hillgaertner discloses a mechanism for adjusting a rear spoiler wing, but the adjustment comprises only raising (deploying) and lowering (stowing) the spoiler wing without any change in angle of attack or shape. U.S. Pat. No. 7,213,870 issued May 8, 2007 to Williams discloses a mechanism for adjusting both the angle of attack and the extent of surface area of a spoiler. However, in all configurations, this spoiler is designed to exert more or less down-thrust behind the rear wheels of the automobile, entailing all the safety, handling and efficiency problems noted above.